Using Moles to Balance Equations (Higher Tier)

This lesson covers how to use experimental mass data and mole calculations to deduce the balanced equation for a reaction, as required by the AQA GCSE Combined Science Trilogy specification (8464) at Higher tier.

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Why Use Moles to Balance Equations?

Sometimes you are given experimental data — masses of reactants and products — and asked to work out the balanced equation. Instead of guessing coefficients, you can calculate the moles of each substance and find the simplest whole-number ratio.

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The Method

flowchart TD
    A["1. Write the correct formulae\nof all reactants and products"] --> B["2. Find the mass of\neach substance"]
    B --> C["3. Calculate the moles of\neach substance using\nmoles = mass ÷ Mr"]
    C --> D["4. Find the simplest\nwhole-number ratio"]
    D --> E["5. Write the balanced\nequation using this ratio"]
    style A fill:#3b82f6,color:#fff,stroke:#2563eb
    style D fill:#f59e0b,color:#000,stroke:#d97706
    style E fill:#22c55e,color:#fff,stroke:#16a34a

Step-by-Step